What Are The Diameters of the Planets? - Universe Today Universe Today What Are The Diameters of the Planets? Article Updated: 1 Jul , 2016 by Matt Williams The planets of our Solar System vary considerably in size and shape. Some planets are small enough that they are comparable in diameter to some of our larger moons – i.e. Mercury is smaller than Jupiter’s moon Ganymede and Saturn’s moon Titan . Meanwhile, others like Jupiter are so big that they are larger in diameter than most of the others combined. In addition, some planets are wider at the equator than they are at the poles. This is due to a combination of the planets composition and their rotational speed. As a result, some planets are almost perfectly spherical while others are oblate spheroids (i.e. experience some flattening at the poles). Let us examine them one by one, shall we? Mercury: With a diameter of 4,879 km (3031.67 mi), Mercury is the smallest planet in our Solar System.

In fact, Mercury is not much larger than Earth’s own Moon – which has a diameter of 3,474 km (2158.64 mi). At 5,268 km (3,273 mi) in diameter, Jupiter’s moon of Ganymede is also larger, as is Saturn’s moon Titan – which is 5,152 km (3201.34 mi) in diameter. Mercury, as imaged by the MESSENGER spacecraft, revealing parts of the never seen by human eyes. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington As with the other planets in the inner Solar System (Venus, Earth, and Mars), Mercury is a terrestrial planet , which means it is composed primarily of metals and silicate rocks that are differentiated into an iron-rich core and a silicate mantle and crust. Also, due to the fact that Mercury has a very slow sidereal rotational period, taking 58.646 days to complete a single rotation on its axis, Mercury experiences no flattening at the poles.

This means that the planet is almost a perfect sphere and has the same diameter whether it is measured from pole to pole or around its equator. Venus: Venus is often referred to as Earth’s “ sister planet “, and not without good reason. At 12,104 km (7521 mi) in diameter, it is almost the same size as Earth. But unlike Earth, Venus experiences no flattening at the poles, which means that it almost perfectly circular. As with Mercury, this is due to Venus’ slow sidereal rotation period, taking 243.025 days to rotate once on its axis. The planet Venus, as imaged by the Magellan 10 mission. Credit: NASA/JPL Earth: With a mean diameter of 12,756 km (7926 mi), Earth is the largest terrestrial planet in the Solar System and the fifth largest planet overall. However, due to flattening at its poles (0.00335), Earth is not a perfect sphere, but an oblate spheroid.

As a result, its polar diameter differs from its equatorial diameter, but only by about 41 km (25.5 mi) In short, Earth measures 12713.6 km (7900 mi) in diameter from pole to pole, and 12756.2 km (7926.3 mi) around its equator. Once again, this is due to Earth’s sidereal rotational period, which takes a relatively short 23 hours, 58 minutes and 4.1 seconds to complete a single rotation on its axis. Mars: Mars is often referred to as “Earth’s twin”; and again, for good reason. Like Earth, Mars experiences flattening at its poles (0.00589), which is due to its relatively rapid sidereal rotational period (24 hours, 37 minutes and 22 seconds, or 1.025957 Earth days). As a result, it experiences a bulge at its equator which leads to a variation of 40 km (25 mi) between its polar radius and equatorial radius.

This works out to Mars having a mean diameter of 6779 km (4212.275 mi), varying between 6752.4 km (4195.75 mi) between its poles and 6792.4 km (4220.6 mi) at its equator. Mosaic of the Valles Marineris hemisphere of Mars, similar to what one would see from orbital distance of 2500 km. Credit: NASA/JPL-Caltech Jupiter: Jupiter is the largest planet in the Solar System, measuring some 142,984 km (88,846 mi) in diameter. Again, this its mean diameter, since Jupiter experiences some rather significant flattening at the poles (0.06487). This is due to its rapid rotational period, with Jupiter taking just 9 hours 55 minutes and 30 seconds to complete a single rotation on its axis. Combined with the fact that Jupiter is a gas giant, this means the planet experiences significant bulging at its equator.

Basically, it varies in diameter from 133,708 km (83,082.3 mi) when measured from pole to pole, and 142,984 km (88,846 mi) when measured around the equator. This is a difference of 9276 km (5763.8 mi), one of the most pronounced in the Solar System. Saturn: With a mean diameter of 120,536 km (74897.6 mi), Saturn is the second largest planet in the Solar System. Like Jupiter, it experiences significant flattening at its poles (0.09796) due to its high rotational velocity (10 hours and 33 minutes) and the fact that it is a gas giant. This means that it varies in diameter from 108,728 km (67560.447 mi) when measured at the poles and 120,536 km (74,897.6 mi) when measured at the equator.

This is a difference of almost 12,000 km, the greatest of all planets. This portrait looking down on Saturn and its rings was created from images obtained by NASA’s Cassini spacecraft on Oct. 10, 2013. Credit: NASA/JPL-Caltech/Space Science Institute/G. Ugarkovic Uranus: Uranus has a mean diameter of 50,724 km (31,518.43 mi), making it the third largest planet in the Solar System. But due to its rapid rotational velocity – the planet takes 17 hours 14 minutes and 24 seconds to complete a single rotation – and its composition, the planet experiences a significant polar flattening (0.0229). This leads to a variation in diameter of 49,946 km (31,035 mi) at the poles and 51,118 km (31763.25 mi) at the equator – a difference of 1172 km (728.25 mi).

Neptune: Lastly, there is Neptune , which has a mean diameter of 49,244 km (30598.8 mi). But like all the other gas giants, this varies due to its rapid rotational period (16 hours, 6 minutes and 36 seconds) and composition, and subsequent flattening at the poles (0.0171). As a result, the planet experiences a variation of 846 km (525.68 mi), measuring 48,682 km (30249.59 mi) at the poles and 49,528 km (30775.27 mi) at the equator. In summary, the planets of our Solar System vary in diameter due to differences in their composition and the speed of their rotation. In short, terrestrial planets tend to be smaller than gas giants, and gas giants tend to spin faster than terrestrial worlds. Between these two factors, the worlds we know range between near-perfect spheres and flattened spheres. For more information of the planets, here is a look at the eight planets and some fact sheets about the planets from NASA.

Astronomy Cast has episodes on all the planets. Here is Mercury to start out with. Share this: Not a planet, Laurele. So Neptune is indeed last. Sorry (not sorry)! laurele Two new planets bigger than Earth ‘found’ in our solar system Two new planets bigger than Earth ‘found’ in our solar system Scientists say discovery would be ‘truly revolutionary for astronomy’ Mon, Jan 19, 2015, 21:18 Updated: Mon, Jan 19, 2015, 22:03 Undated handout artist impression of one of the two as-yet undiscovered planets as big as Earth or larger may be hiding in the outer fringes of the Solar System, scientists believe. Photograph: PA Schoolchildren may need a new mnemonic to remember the sequence of planets as astronomers now believe there may be at least two ‘new’ planets in our solar system. The two planets – which may both be bigger than earth – could be orbiting in the furthest reaches of the solar system out past Pluto, which was demoted from the status of planet to a dwarf planet in 2006.

The discovery of possible new additions to our existing eight planets, if confirmed, has been described by one of the scientists involved as “truly revolutionary for astronomy”. The research is being carried out by from scientists at the University of Madrid and the University of Cambridge. They have been tracking large asteroids known as “extreme trans-Neptunion objects” (Etnos) which orbit the sun at least six billion kilometres away. The scientists have found the objects orbit the Sun in a manner consistent with them being subject to the gravitational pull of a planet at least as large as Earth. Neptune was discovered in a similar fashion when astronomers accurately calculated its existence from irregularities in the orbit of its neighbouring planet Uranus. Spanish lead scientist Professor Carlos de la Fuente Marcos, from the Complutense University of Madrid (UCM), explained: “This excess of objects with unexpected orbital parameters makes us believe that some invisible forces are altering the distribution of the orbital elements of the Etnos, and we consider that the most probable explanation is that other unknown planets exist beyond.” Professor Marcos concluded that there are at least two planets “and probably more within the confines of our solar system”. Though more data was needed, the possibilities were “truly revolutionary”, he added.

The new research, published in the journal Monthly Notices of the Royal Astronomical Society Letters, is based on analysis of an effect called the “Kozai mechanism”, by which a large body disturbs the orbit of a smaller and more distant object. ADVERTISEMENT The scientists wrote: “In this scenario, a population of stable asteroids may be shepherded by a distant, undiscovered planet larger than the Earth”. The “super Earths” as they have been described are orbiting at 250AU (astronomical units) from the sun, a distance of almost 40 billion kilometres. At such distances, the planets would reflect so little light from the sun that they would be invisible even to the most sensitive telescope. Planet Jupiter: Facts About Its Size, Moons and Red Spot Planet Jupiter: Facts About Its Size, Moons and Red Spot By Charles Q. Choi, Space.com Contributor | November 14, 2014 12:59am ET MORE This photo of Jupiter was taken on Sept. 20, 2010 when Jupiter made its closest approach to Earth since 1963.

(Uranus [insert] was visible through telescopes near Jupiter.) Credit: Jimmy Eubanks Jupiter is the largest planet in the solar system. Fittingly, it was named after the king of the gods in Roman mythology. In a similar manner, the ancient Greeks named the planet after Zeus, the king of the Greek pantheon. Jupiter helped revolutionize the way we saw the universe and ourselves in 1610, when Galileo discovered Jupiter's four large moons — Io, Europa, Ganymede and Callisto, now known as the Galilean moons. This was the first time celestial bodies were seen circling an object other than Earth, major support of the Copernican view that Earth was not the center of the universe. Physical characteristics Jupiter is the most massive planet in our solar system , more than twice as massive as all the other planets combined, and had it been about 80 times more massive, it would have actually become a star instead of a planet. Its atmosphere resembles that of the sun, made up mostly of hydrogen and helium, and with four large moons and many smaller moons in orbit around it, Jupiter by itself forms a kind of miniature solar system.

All told, the immense volume of Jupiter could hold more than 1,300 Earths. The colorful bands of Jupiter are arranged in dark belts and light zones created by strong east-west winds in the planet's upper atmosphere traveling more than 400 mph (640 kph). The white clouds in the zones are made of crystals of frozen ammonia, while darker clouds of other chemicals are found in the belts. At the deepest visible levels are blue clouds. Far from being static, the stripes of clouds change over time . Inside the atmosphere, diamond rain may fill the skies. The most extraordinary feature on Jupiter is undoubtedly the Great Red Spot , a giant hurricane-like storm seen for more than 300 years. At its widest, the Great Red Spot is three times the diameter of the Earth, and its edge spins counterclockwise around its center at a speed of about 225 mph (360 kph). The color of the storm, which usually varies from brick red to slightly brown, may come from small amounts of sulfur and phosphorus in the ammonia crystals in Jupiter's clouds. The spot grows and shrinks over time, and every now and again, seems to fade entirely.

Jupiter's gargantuan magnetic field is the strongest of all the planets in the solar system at nearly 20,000 times the strength of Earth's. It traps electrically charged particles in an intense belt of electrons and other electrically charged particles that regularly blasts the planet's moons and rings with a level of radiation more than 1,000 times the lethal level for a human, damaging even heavily shielded spacecraft such as NASA's Galileo probe. The magnetosphere of Jupiter, which is composed of these fields and particles, swells out some 600,000 to 2 million miles (1 million to 3 million km) toward the sun and tapers to a tail extending more than 600 million miles (1 billion km) behind Jupiter. Jupiter spins faster than any other planet, taking a little under 10 hours to complete a turn on its axis, compared with 24 hours for Earth. This rapid spin makes Jupiter bulge at the equator and flatten at the poles, making the planet about 7 percent wider at the equator than at the poles. Jupiter broadcasts radio waves strong enough to detect on Earth.

These come in two forms — strong bursts that occur when Io, the closest of Jupiter's large moons, passes through certain regions of Jupiter's magnetic field, and continuous radiation from Jupiter's surface and high-energy particles in its radiation belts. These radio waves could help scientists to probe the oceans on its moons. Composition & structure Atmospheric composition (by volume): 89.8 percent molecular hydrogen, 10.2 percent helium, minor amounts of methane, ammonia, hydrogen deuteride, ethane, water, ammonia ice aerosols, water ice aerosols, ammonia hydrosulfide aerosols Magnetic field: Nearly 20,000 times stronger than Earth's Chemical composition: Jupiter has a dense core of uncertain composition , surrounded by a helium-rich layer of fluid metallic hydrogen, wrapped up in an atmosphere primarily made of molecular hydrogen. Internal structure: A core less than 10 times Earth's mass surrounded by a layer of fluid metallic hydrogen extending out to 80 to 90 percent of the diameter of the planet, enclosed in an atmosphere mostly made of gaseous and liquid hydrogen.

Orbit & rotation Average distance from the sun : 483,682,810 miles (778,412,020 km). By comparison: 5.203 times that of Earth Perihelion (closest approach to the sun): 460,276,100 miles (740,742,600 km). By comparison: 5.036 times that of Earth Aphelion (farthest distance from the sun): 507,089,500 miles (816,081,400 km). By comparison: 5.366 times that of Earth (Source: NASA .) Jupiter's moons Jupiter has at least 63 moons , which are often named after the Roman god's many lovers. The four largest moons of Jupiter, now called Io, Europa, Ganymede, and Callisto, were discovered by Galileo Galilei himself, and are appropriately known today as the Galilean satellites. Ganymede is the largest moon in our solar system, larger even than Mercury and Pluto.

It is also the only moon known to have its own magnetic field. The moon has at least one thick ocean between layers of ice, although it may contain several layers of both materials. Io is the most volcanically active body in our solar system. The sulfur its volcanoes spew out gives Io a blotted yellow-orange appearance that is often compared to a pepperoni pizza. As Io orbits Jupiter, the planet's immense gravity causes 'tides' in Io's solid surface that rise 300 feet (100 meters) high, generating enough heat for volcanic activity. The frozen crust of Europa is made up mostly of water ice, and it may hide a liquid ocean holding twice as much water as Earth does. Icy oceans may also exist beneath the crusts of Callisto and Ganymede. Some of this liquid spouts from the surface in newly spotted sporadic plumes at the southern pole. Its potential to host life caused NASA to request funding for a mission to explore Europa . Callisto has the lowest reflectivity, or albedo, of the four Galilean moons. This suggests that its surface may be composed of dark, colorless rock.

Jupiter's rings Jupiter's three rings came as a surprise when NASA's Voyager 1 spacecraft discovered them around the planet's equator in 1979. Each are much fainter than Saturn's rings. The main ring is flattened. It is about 20 miles (30 km) thick and more than 4,000 miles (6,400 km) wide. The inner cloud-like ring, called the halo, is roughly 12,000 miles (20,000 km) thick. The halo extends halfway from the main ring down to the planet's cloud tops and expands by interaction with Jupiter's magnetic field. Both the main ring and halo are composed of small, dark particles. The third ring, known as the gossamer ring because of its transparency, is actually three rings of microscopic debris from three of Jupiter's moons, Amalthea, Thebe and Adrastea.

It is probably made up of dust particles less than 10 microns in diameter, about the same size of the particles found in cigarette smoke, and extends to an outer edge of about 80,000 miles (129,000 km) from the center of the planet and inward to about 18,600 miles (30,000 km). Ripples in the rings of both Jupiter and Saturn may be signs of impacts from comets and asteroids. Research & exploration Seven missions have flown by Jupiter — Pioneer 10 , Pioneer 11 , Voyager 1 , Voyager 2 , Ulysses, Cassini and New Horizons — while another, NASA's Galileo, actually orbited the planet. Pioneer 10 revealed how dangerous Jupiter's radiation belt is, while Pioneer 11 provided data on the Great Red Spot and close-up pictures of its polar region. Voyager 1 and 2 helped astronomers create the first detailed maps of the Galilean satellites, discovered Jupiter's rings, revealed sulfur volcanoes on Io, and saw lightning in Jupiter's clouds.

Ulysses discovered the solar wind has a much greater impact on Jupiter's magnetosphere than before suggested. New Horizons took close-up pictures of Jupiter and its largest moons. In 1995, Galileo sent a probe plunging towards Jupiter, making the first direct measurements of its atmosphere and measuring the amount of water and other chemicals there. When Galileo ran low on fuel, the craft was intentionally crashed into Jupiter's atmosphere to avoid any risk of it slamming into and contaminating Europa, which might have an ocean below its surface capable of supporting life. Another spacecraft, named Juno , is heading toward Jupiter and will reach the planet in 2016. It will study Jupiter from a polar orbit to figure out how it and the rest of the solar system formed, which could shed light on how alien planetary systems might have developed. Jupiter's gravitational impact on the solar system As the most massive body in the solar system after the sun, the pull of Jupiter's gravity has helped shape the fate of our system. It may have violently hurled Neptune and Uranus outward , according to calculations published in the journal Nature.

Jupiter, along with Saturn, may have slung a barrage of debris toward the inner planets early in the system's history, according to an article in Science magazine. It may even nowadays help keep asteroids from bombarding Earth, and recent events certainly have shown that it can absorb potentially deadly impacts . Currently, Jupiter's gravitational field influences numerous asteroids that have clustered into the regions preceding and following Jupiter in its orbit around the sun. These are known as the Trojan asteroids, after three large asteroids there, Agamemnon, Achilles and Hector, names drawn from the Iliad, Homer's epic about the Trojan War. Possibility of life on Jupiter If one were to dive into Jupiter's atmosphere , one would discover it to grow warmer with depth, reaching room temperature, or 70 degrees F (21 degrees C), at an altitude where the atmospheric pressure is about 10 times as great as it is on Earth. Scientists have conjectured that if Jupiter has any form of life, it might dwell at this level, and would have to be airborne. However, researchers have found no evidence for life on Jupiter.

Additional reporting by Nola Taylor Redd, Space.com Contributor Explore the solar system Two Planets Larger Than Earth May Exist Beyond Pluto Two Planets Larger Than Earth May Exist Beyond Pluto By Paula Mejia On 1/17/15 at 2:18 PM A visitor looks at a model of the solar system, including Pluto (lower R), at the Boston's Museum of Science in Boston, Massachusetts. Brian Snyder/Reuters Tech & Science Out past Pluto, in a galaxy not that far, far away (ours, in fact), may lie two planets larger than Earth. Astrophysicists studying “extreme trans-Neptunian objects” (ETNOs) now believe that a “Planet X” and a “Planet Y” are ripe for discovery, reports Space.com . If proven to be true, it will significantly alter what we currently believe about the solar system. The research, published this week via two papers in the Monthly Notices of the Royal Astronomical Society Letters journal, was conducted by astronomers at the University of Cambridge and the Complutense University of Madrid.

In calculating the orbits of 13 ETNOs around Pluto, whose unique gravitational pull influences orbits of objects beyond Neptune, the scientist came to believe the orbit patterns indicate that another force is also acting upon the ETNOs. Perhaps, they said, it could even be an “icy super-Earth” that is 10 times larger than our Blue Marble. Carlos de la Fuente Marcos, an astrophysicist at the UCM and co-author of the study, said: "The exact number is uncertain, given that the data that we have is limited, but our calculations suggest that there are at least two planets, and probably more, within the confines of our solar system.” Try Newsweek for only $1.25 per week This discovery could very well change the face of astronomy as we know it, as the data contradicts our contemporary solar models, which don’t account for planets past Neptune. But the paper’s authors were careful to mention that their research was conducted on only a handful of space bodies, and said they expect to examine a larger area in the coming months.

Related Stories Planetary Hunt Yields Four New ‘Earth Twins’ Critics of the discovery have also commented on the data’s small sample size, as well as a lack of concrete observations of the theoretical new planets, X and Y. So while there may be more planets out there, the data isn’t there to fully support such claims just yet. Major Discovery: New Planet Could Harbor Water and Life Major Discovery: New Planet Could Harbor Water and Life By Ker Than | April 24, 2007 04:23pm ET MORE One of the several planets within the Gliese 581 star system, called Gliese 581 d, may be one of the most potentially habitable alien worlds known. It is about 8 times the mass of Earth, and located in an orbit just right for liquid water to exist on the surface. Water is a key ingredient for life as we know it. Gliese 581 is a red dwarf star 20.5 light-years from Earth Credit: ESO An Earth-like planet spotted outside our solar system is the first found that could support liquid water and harbor life, scientists announced today. Liquid water is a key ingredient for life as we know it.

The newfound planet is located at the "Goldilocks" distance-not too close and not too far from its star to keep water on its surface from freezing or vaporizing away. And while astronomers are not yet able to look for signs of biology on the planet, the discovery is a milestone in planet detection and the search for extraterrestrial life, one with the potential to profoundly change our outlook on the universe. "The goal is to find life on a planet like the Earth around a star like the Sun. This is a step in that direction," said study leader Stephane Udry of the Geneva Observatory in Switzerland. "Each time you go one step forward you are very happy." The new planet is about 50 percent bigger than Earth and about five times more massive. The new "super-Earth" is called Gliese 581 C, after its star, Gliese 581, a diminutive red dwarf star located 20.5 light-years away that is about one-third as massive as the Sun. Smallest to date Gliese 581 C is the smallest extrasolar planet, or "exoplanet," discovered to date.

It is located about 15 times closer to its star than Earth is to the Sun; one year on the planet is equal to 13 Earth days. Because red dwarfs, also known as M dwarfs, are about 50 times dimmer than the Sun and much cooler, their planets can orbit much closer to them while still remaining within their habitable zones , the spherical region around a star within which a planet's temperature can sustain liquid water on its surface. Because it lies within its star's habitable zone and is relatively close to Earth, Gliese 581 C could be a very important target for future space missions dedicated to the search for extraterrestrial life, said study team member Xavier Delfosse of Grenoble University in France. "On the treasure map of the universe, one would be tempted to mark this planet with an X," Delfosse said. Two other planets are known to inhabit the red dwarf system. One is a 15 Earth-mass " hot-Jupiter " gas planet discovered by the same team two years ago, which orbits even closer to its star than does Gliese 581 C.

Another is an 8 Earth-mass planet discovered at the same time as Gliese 581 C, but which lies outside its star's habitable zone. Possible waterworld Computer models predict Gliese 581 C is either a rocky planet like Earth or a waterworld covered entirely by oceans. "We have estimated that the mean temperature of this super-Earth lies between 0 and 40 degrees Celsius [32 to 104 degrees Fahrenheit], and water would thus be liquid," Udry said. The scientists discovered the new world using the HARP instrument on the European Southern Observatory 3.6 meter telescope in La Sille, Chile. They employed the so-called radial velocity, or "wobble," technique, in which the size and mass of a planet are determined based on small perturbations it induces in its parent star's orbit via gravity. Udry said there was a fair amount of time between the calculation of Gliese 581 C's size and the realization it was within its star's habitable zone. "That came at the end," Udry said. When it did hit him, Udry knew he would be spending time fielding phone calls from the media.

"You right away think about the journalists who will like it very much," he told SPACE.com. More to come David Charbonneau, an astronomer at the Harvard-Smithsonian Center for Astrophysics (CfA) who was not involved in the study, said the new finding is an "absolutely fantastic discovery." "It means there probably are many more such planets out there ," Charbonneau said in a telephone interview. Whether Gliese 581 C harbors life is still unknown, but "it satisfies for the first time a key requirement." Charbonneau also praised the team's technical skills. "The wobble induced on the star by each of these planets is really tiny-it's just a few meters a second. That means their measurement precision is exquisite," he said. David Latham, another astronomer at Harvard-Smithsonian CfA, echoed other scientists' praise of the discovery but said the next step is to find a similar world where the orbit of the habitable planet carries it between Earth and its parent star. This will allow scientists to observe it using the transit technique, whereby the small dimming starlight caused by the planet's passage across the face of its sun can be used to calculate its size.

Only then can scientists determine for certain whether the world is rocky or covered by water, Latham said. Alan Boss, a planetary theorist at the Carnegie Institution of Washington, said the new planet's potential for liquid water made it "fascinating." Gliese 581 C "is the closest planet to another Earth that has been found to date. I hope the SETI folks are listening," Boss said. Seth Shostak, a senior astronomer at the SETI institute, said the Gliese 581 system has in fact been looked at twice before for signs of intelligent life. The first time was in 1995 using the Parkes Radio Telescope in Australia; the second time occured in 1997 using the 140-foot telescope in Greenbank,West Virgina. Both times revealed nothing. "It has been looked at twice, but that doesn't mean we shouldn't look at it again," Shostak said. "And indeed we should because this is the best candidate the extrasolar planet guys have come up with yet." Shostak said he was "jazzed" by the discovery.

"This is pointing to something that in the past has only been an assumption, namely that Earth-sized worlds are not rare," he said. "We know of only two [planets in the habitable zone]. We know this one and we know our own. But two is better than one." Shostak said the Gliese 581 system will likely be looked at again over much wider range of the radio spectrum when the new Allen Telescope Array begins operations this summer. "You could say it's going to the head of the class," he said. Video: A World Like Our Own Planet bigger than Earth in our solar system? | KSDK.com Planet bigger than Earth in our solar system? Traci Watson , KSDK 6:28 PM. CDT March 26, 2014 IN SPACE: In this Caltech undated handout, a rendering of the farthest object in our solar system, Sedna, is seen. Sedna is a mysterious planet-like body three times farther from Earth than Pluto. NASA held a news conference March 15, 2004 to detail the findings by a team of astronomers at Caltech led by Dr. Mike Brown.

(Photo: Getty Images Getty Images) CONNECT TWEET LINKEDIN GOOGLE+ PINTEREST Scientists say they've found a pink dwarf planet that travels farther from the sun than anything ever seen. Its discovery has led to tantalizing hints that a separate, unknown planet bigger than the Earth lurks at the fringes of the solar system, exerting a stealthy control over its neighbors. The new planet is a celestial bonbon, a dainty, rose-colored ice ball far smaller than tiny Pluto. Its detection helps confirm that the outer stretches of the solar system are a crowded place. An analysis of its orbit and the orbits of other heavenly bodies provides evidence for a super-sized planet at least 200 times as far from the sun as the Earth is. The analysis, if correct, shows "there needs to be another planet out there, which is really amazing," says Scott Kenyon of the Smithsonian Astrophysical Observatory, who was not involved in the new research. "Adding an Earth-mass planet … will change a lot of people's thinking." The possibility of a new super-Earth arose from scientists' campaign to find objects beyond the orbit of Pluto, in some of the chilliest, most distant reaches of the solar system.

The only known body in that no-man's land is the dwarf planet Sedna. Found in 2003, it's twice as far from the sun as any other object detected in the solar system. A decade later, researchers spotted Sedna's first known neighbor. It's officially called 2012 VP-113, but the "VP" inspired the nickname "Biden." Unlike its namesake, it's petite, measuring roughly 20% as wide as Pluto. Biden travels a cold, remote path, coming no closer to the sun than 7.4 billion miles, vs. Sedna's closest approach of 7.1 billion miles. Calculations show Biden and Sedna must have roughly 900 good-sized undiscovered neighbors, scientists report in this week's Nature. After the discovery of Sedna, "finding the second object shows there is a big population out there," says study co-author Scott Sheppard of the Carnegie Institution for Science.

"Our solar system has a very rich inventory of planetesimals, and we've only just touched the tip of the iceberg here in finding these objects." Something strange emerged when Sheppard and his colleague, Chadwick Trujillo of the Gemini Observatory, compiled data for the orbits of Sedna, Biden and 10 icy objects that lie close to Pluto. Similarities in the 12 objects' paths around the sun strongly suggest that all 12 are under the spell of a hulking, far-distant planet, Sheppard says. This planet, if it exists, is up to 10 times as massive as Earth and 200 to 1,000 times as far from the sun. It's so big that it has forced the smaller bodies, which like to keep away from large ones, into unexpected paths. This super-Earth may have begun its life in the central solar system before becoming a "rogue planet," ejected from its birthplace to exile in the outermost solar system. Like some celestial Pied Piper, it may have pulled Sedna and Biden along with it from their homes closer to the sun. Other scientists disagree on the plausibility of a large planet haunting the distant stretches of the solar system.

"It's a fun possibility to consider, but I would say it's pretty speculative," says Sedna co-discoverer Michael Brown of the California Institute of Technology. He expects researchers will "come up with 100 different, more mundane reasons why this arrangement could be like that." Perhaps the data could be explained by coincidence, says Harold Levison of the Southwest Research Institute in Colorado. Levison says that although he remains to be convinced, this proposal for a rogue planet is "surprising and almost believable." His reaction to previous reports of rogue planets has always been "b.s.," Levison says. "I've never been seduced by any of those arguments, except this one. … If that data's right, I can't think of any other way to explain it." The Planets in Our Solar System in Order of Size - Universe Today Universe Today The Planets in Our Solar System in Order of Size Article Updated: 23 Dec , 2015 by Elizabeth Howell If you’re interested in planets, the good news is there’s plenty of variety to choose from in our own Solar System.

From the ringed beauty of Saturn, to the massive hulk of Jupiter, to the lead-melting temperatures on Venus, each planet in our solar system is unique — with its own environment and own story to tell about the history of our Solar System. What also is amazing is the sheer size difference of planets. While humans think of Earth as a large planet, in reality it is dwarfed by the massive gas giants lurking at the outer edges of our Solar System. This article explores the planets in order of size, with a bit of context as to how they got that way. A short history of the Solar System No human was around 4.5 billion years ago when the Solar System was formed, so what we know about its birth comes from several sources: examining rocks on Earth and other places, looking at other solar systems in formation and doing computer models, among other methods. As more information comes in, some of our theories of the Solar System must change to suit the new evidence. Today, scientists believe the Solar System began with a spinning gas and dust cloud. Gravitational attraction at its center eventually collapsed to form the Sun.

Some theories say that the young Sun’s energy began pushing the lighter particles of gas away, while larger, more solid particles such as dust remained closer in. Artist’s conception of a solar system in formation. Credit: NASA/FUSE/Lynette Cook Over millions and millions of years, the gas and dust particles became attracted to each other by their mutual gravities and began to combine or crash. As larger balls of matter formed, they swept the smaller particles away and eventually cleared their orbits. That led to the birth of Earth and the other eight planets in our Solar System. Since much of the gas ended up in the outer parts of the system, this may explain why there are gas giants — although this presumption may not be true for other solar systems discovered in the universe. Until the 1990s, scientists only knew of planets in our own Solar System and at that point accepted there were nine planets. As telescope technology improved, however, two things happened. Scientists discovered exoplanets, or planets that are outside of our solar system. This began with finding massive planets many times larger than Jupiter, and then eventually finding planets that are rocky — even a few that are close to Earth’s size itself .

The other change was finding worlds similar to Pluto, then considered the Solar System’s furthest planet, far out in our own Solar System. At first astronomers began treating these new worlds like planets, but as more information came in, the International Astronomical Union held a meeting to better figure out the definition. Hubble image of Pluto and some of its moons, Charon, Nix and Hydra. Image Credit: NASA, ESA, H. Weaver (JHU/APL), A. Stern (SwRI), and the HST Pluto Companion Search Team The result was redefining Pluto and worlds like it as a dwarf planet. This is the current IAU planet definition: “A celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.” Size of the eight planets According to NASA , this is the estimated radii of the eight planets in our solar system, in order of size. We also have included the radii sizes relative to Earth to help you picture them better.

Jupiter (69,911 km / 43,441 miles) – 1,120% the size of Earth Saturn (58,232 km / 36,184 miles) – 945% the size of Earth Uranus (25,362 km / 15,759 miles) – 400% the size of Earth Neptune (24,622 km / 15,299 miles) – 388% the size of Earth Earth (6,371 km / 3,959 miles) Venus (6,052 km / 3,761 miles) – 95% the size of Earth Mars (3,390 km / 2,460 miles) – 53% the size of Earth Mercury (2,440 km / 1,516 miles) – 38% the size of Earth Eight planets and a dwarf planet in our Solar System, approximately to scale. Pluto is a dwarf planet at far right. At far left is the Sun.

The planets are, from left, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Credit: Lunar and Planetary Institute Jupiter is the behemoth of the Solar System and is believed to be responsible for influencing the path of smaller objects that drift by its massive bulk. Sometimes it will send comets or asteroids into the inner solar system, and sometimes it will divert those away. Saturn, most famous for its rings, also hosts dozens of moons — including Titan, which has its own atmosphere. Joining it in the outer solar system are Uranus and Neptune, which both have atmospheres of hydrogen, helium and methane. Uranus also rotates opposite to other planets in the solar system. The inner planets include Venus (once considered Earth’s twin, at least until its hot surface was discovered); Mars (a planet where liquid water could have flowed in the past); Mercury (which despite being close to the sun, has ice at its poles) and Earth, the only planet known so far to have life.

To learn more about the Solar System, check out these resources: Huge distant planet has rings 200 times larger than Saturn's | Science Wire | EarthSky Huge distant planet has rings 200 times larger than Saturn’s By Eleanor Imster in Science Wire | Space | January 29, 2015 It’s a super Saturn, 434 light-years from Earth. It has more than 30 rings, with a total diameter of some 120 million kilometers. If we could replace Saturn’s rings with these rings, they’d be easily visible from Earth and larger in our sky than a full moon. Artist’s concept of the ring system around the young giant planet or brown dwarf J1407b. Image via Ron Miller An international team of astronomers have discovered that a ring system around a distant planet – called J1407b – is of enormous proportions, much larger and heavier than the ring system of Saturn. The planet orbits star J1407, located approximately 434 light-years from Earth. Astronomers first identified the ring system – the first of its kind to be found outside our solar system – in 2012.

A new analysis of the data, published in the Astrophysical Journal, shows that the ring system consists of more than 30 rings, each of them tens of millions of kilometers in diameter. Furthermore, the analysis found gaps in the rings, which indicate that satellites (“exomoons”) may have formed. Erik Mamajek is a professor of physics and astronomy at the University of Rochester and a co-author of the ring study. He said: This planet is much larger than Jupiter or Saturn, and its ring system is roughly 200 times larger than Saturn’s rings are today. You could think of it as kind of a super Saturn. If the enormous ring system around J1407b’s replaced the rings of Saturn in our solar system, they’d be visible at night to the unaided eye, with many times the diameter of a full moon. Illustration via M. Kenworthy/Leiden. The disk of rings is so vast that, were it around Saturn, it would dominate our night sky, the astronomers said.

According to Matthew Kenworthy of the Leiden Observatory in The Netherlands: If we could replace Saturn’s rings with the rings around J1407b, they would be easily visible at night and be many times larger than the full moon. Mamajek put into context how much material is contained in these disks and rings: If you were to grind up the four large Galilean moons of Jupiter into dust and ice and spread out the material over their orbits in a ring around Jupiter, the ring would be so opaque to light that a distant observer that saw the ring pass in front of the sun would see a very deep, multi-day eclipse. In the case of J1407, we see the rings blocking as much as 95 percent of the light of this young Sun-like star for days, so there is a lot of material there that could then form satellites. Astronomers expect that the rings will become thinner in the next several million years and eventually disappear as satellites form from the material in the disks. Bottom line: First-ever ringed planet beyond our solar system. You could think of it as kind of a super Saturn.

Called J1407b, its ring system is 200 times larger than Saturn’s.

Question: How many planets in the Solar System are bigger than Earth
Answer: Four